3-Substituent effect and 3-methylene substituent effect on the structure-reactivity relationship of 7.beta.-(acylamino)-3-cephem-4-carboxylic acid derivatives studied by carbon-13 and IR spectroscopy

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Abstract
Relationships between the chemical reactivity of 3-substituted cephalosporins [antibacterial drugs] or 3-methylene-substituted cephalosporins and several parameters observed by 13C NMR and IR spectroscopies are described. Among 3-substituted cephalosporins, the values of .delta.(C-3) and .delta.(COO) of 13C NMR spectra are correlated with the logarithms of the rate constants for alkaline hydrolysis (log kobsd) when substituents at the 3-position are classified into 2 groups, i.e., OR substituents and others. Among the 3-methylene-substituted cephalosporins, the difference values of the 13C chemical shifts for C-3 and C-4, .DELTA..delta.(4-3), are correlated with log kobsd. The .beta.-lactam vc.dbd.o value of the solution IR spectra is a good index for the prediction of a significant change of the .beta.-lactam reactivity resulting from modification of a 3-substituent or a 3-methylene sustituent. From analysis of these observed parameters, both resonance and inductive effects of the substitutent at the 3-position affected the chemical reactivity of the .beta.-lactam ring in cephalosporin, while only the inductive effect of the substituent at the 3''-position affected the .beta.-lactam reactivity.

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